There are x balls in a box, of which 20% are red balls and the rest are blue balls. If 10 blue balls are taken out , 60% of the ball in the box are blue ball. Find x.
I am so confused with the question, could anyone help me to solve the problem? thx!
percentage's problem
2009-07-14 6:33 am
回答 (2)
2009-07-14 6:50 am
✔ 最佳答案
There are x balls in the box.Number of red balls = 0.2x
Number of blue balls = 0.8x
After taking out 10 blue balls, there are still 0.8x - 10 blue balls
Total number of balls that remains = x-10
Percentage of blue balls then becomes
(0.8x -10)/(x -10) = 0.6
0.8x - 10 = 0.6x -6
0.2x = 4
x=20
2009-07-14 7:15 am
明啦! thanks!
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